ASTM F3125 Grade A325 heavy hex bolts are high strength structural bolts manufactured from medium carbon steel, carbon boron, or medium carbon alloy steel. A325 hex bolts are available in diameters from 1/2" through 1 1/2" inclusive. Dimensional specifications are governed by ASME B18.2.6. Grade markings consists of both the grade symbol "A325" and the manufacturer's identification mark. Inch series fasteners meeting ASTM F3125 Grade A325 specifications are intended for use in steel to steel structural connections. Grade A325 heavy hex bolts offer a heavy pattern head to increase the bearing surface and distribute the clamping load over a larger area.